Grazing with heifers and sows alone or mixed: herbage quality, sward structure and animal weight gain

The aim of the present study was to compare the effect of mixed grazing (MI) by sows and heifers with alternate grazing (AL) or grazing heifers (HN) and sows (SN) alone on animal weight gain, sward structure, herbage quality and composition, and selection during grazing. Mixed or alternate grazing consistently improved the weight gain in both heifers and sows, compared with grazing one species alone, but the positive effect was statistically significant only for heifers. The herbage quality of the MI and AL systems was better compared with the SN system, but not clearly better compared with the HN system. The total animal weight gain (heifers + sows) and estimated herbage intake per hectare were also higher in the MI and AL systems compared with SN and HN systems. The sows grazed selectively as they preferred clover rather than grass and grass leaves rather than grass stem. Only few turnovers of the sward by the sows were observed. Animal behaviour was not systematically surveyed, but no adverse behaviour was observed between the two animal species. Herbage quality, proportion of rejected herbage and the load of gastro-intestinal nematodes in heifers could have positively influenced animal weight gain per day and hectare in the MI and AL systems in this study. (C) 2004 Elsevier B.V. All rights reserved.